1. Field of the Invention
The present invention relates to a printing apparatus in which the print head travels orthogonally to the direction in which the printing medium travels in order to print to the printing medium. More specifically, the present invention relates to a printing apparatus having a novel means for preventing paper jams accompanying movement of the print head, a control method for the printing apparatus, and a data storage medium storing the control method of the invention.
2. Description of the Related Art
Impact printers, thermal printers, inkjet printers, and other printers that print by moving a carriage-mounted print head orthogonally to the direction in which the printing medium travels are widely used and commonly available. Most printers used in conjunction with cash registers and point-of-sale terminals for printing slip forms are of this type. This category of printers includes printers requiring the user to place the printing form at a particular location in the printing unit. Such printers have an openable/closable transportation roller for clamping and holding the form for printing. When the user then initiates printing and a print command is sent from the host device to the printer, the transportation roller closes to clamp and hold the form. The transportation roller is then driven to advance the form into the printing unit, and printing begins.
As taught by Japan Unexamined Utility Model Publication (jikkai) 5-68989, this type of printer can automatically eject any medium present in the transportation path when the power is turned on as a means of preventing paper jams.
When a xe2x80x9creturn homexe2x80x9d or similar command is received from the host after the power is turned on and a form is set in the printing unit, the carriage in this type of printer moves across the form to the standby position, known as the home position. The form, however, may be wrinkled, have folded corners, or otherwise be raised off of the platen and interfere with print head movement at this time because the form is not clamped by the transportation roller. The carriage may therefore catch on the form or tear the form, resulting in a paper jam.
This is a particular problem in printers having a straight transportation path for printing to slip forms. In printers with a curved transportation path the curves in the transportation path increase the stiffness of the printing medium, and help to keep the printing medium away from the carriage path. This is not the case in printers with a straight transportation path, and the loose printing medium thus tends to wander into the path of the print head carriage.
There is therefore a need for a printing apparatus whereby paper jams and damage to the printing medium can be prevented by either constantly clamping the printing medium with a transportation roller when the print head carriage moves, or ejecting the printing medium before carriage movement.
Therefore, it is an object of the present invention to overcome the aforementioned problems.
It is a another object of the present invention to provide a printing apparatus that includes a transportation roller mechanism that holds the printing medium whenever the carriage on which a print head is mounted moves to prevent the printing medium from protruding into the path of the carriage and causing paper jams and/or damage to the printing medium.
The present invention addresses the above-noted need by providing a printing apparatus for printing to a printing medium by moving a print head orthogonally to the direction in which the printing medium is transported along a transportation path to a printing unit. More specifically, a printing apparatus according to the present invention comprises a transportation roller pair selectively movable between an open position and a closed position in which the transportation roller pair holds and transports the printing medium along the transportation path to the printing unit, and a driver to open and close the transportation roller pair based on a control command. When a control command involving print head movement is received, the driver is controlled to close the transportation roller pair. As a result, the printing medium is always held by the transportation roller pair when the print head moves.
Control commands involving print head movement (simply xe2x80x9ccommandsxe2x80x9d below) include, for example, a return home command moving the print head to a standby position, and printer initialization commands.
The printing apparatus according to the present invention can further comprise a medium detector to detect if the printing medium is inserted in the transportation path. In this case, the driver is controlled to close the transportation roller pair only when insertion of the printing medium has been detected by the medium detector as being correctly positioned. The transportation roller pair is thus not closed when the printing medium is not present in the transportation path, and noise accompanying transportation roller operation can be reduced.
The driver can be further controlled to open the transportation roller pair after closing the transportation roller pair and executing a control command involving print head movement. This enables the user to remove and reinsert a printing medium as necessary or desired.
The printing apparatus according to the present invention can further comprise a medium position detector to detect if the printing medium is correctly positioned in the transportation path. In this case, the driver is controlled to not open the transportation roller pair when the printing medium is correctly positioned after closing the transportation roller pair and executing a control command involving print head movement, and to otherwise open the transportation roller pair. Whether the printing medium is correctly positioned or not can be determined using a medium leading edge detector to detect the leading edge of the printing medium, and a medium side edge detector to detect the side edge of the printing medium.
The printing apparatus of the invention can be further comprised to drive the transportation roller pair and eject the printing medium after closing the transportation rollers. In this case, the printing medium is preferably ejected to the open insertion side of the transportation path.
By thus controlling the driver to open the transportation roller pair after ejecting the printing medium and implementing a control command involving print head movement, the user can reinsert the printing medium as necessary or desired.
The present invention is particularly suited to printing apparatuses having a relatively straight printing medium transportation path.
The present invention further addresses the above-noted need by providing a control method for a printing apparatus. The printing apparatus in this case prints to a printing medium by moving a print head orthogonally to the transportation direction of the printing medium, and comprises a transportation roller pair selectively movable between an open position and a closed position in which the transportation roller pair holds and transports the printing medium to the printing unit, and a driver to open and close the transportation roller pair based on a control command. The control method comprises controlling the driver to close the transportation roller pair when a control command involving print head movement is received, and moving the print head according to the control command.
The invention further provides a control method for a printing apparatus for printing to a printing medium by moving a print head orthogonally to the transportation direction of the printing medium. The printing apparatus comprises a transportation roller pair selectively movable between an open position and a closed position in which the transportation roller pair holds and transports the printing medium to the printing unit, a driver to open and close the transportation roller pair based on a control command, and a medium detector to detect if a printing medium is correctly positioned in the transportation path. The control method in this case comprises detecting whether the printing medium is inserted in the transportation path using the medium detector when a control command involving print head movement is received, controlling the driver to close the transportation roller pair when the printing medium is correctly positioned and detected, and moving the print head according to the control command.
The control method of the invention further preferably comprises controlling the driver to not open the transportation roller pair when the printing medium is correctly positioned based on the detection result of the medium position detector, and otherwise controlling the driver to open the transportation roller pair.
The control method of the invention yet further preferably comprises ejecting the printing medium using the transportation roller pair after controlling the driver to close the transportation roller pair.
The control method of the invention can also be provided as a control program for controlling a printing apparatus, and the control program can be recorded and stored on any computer-readable storage medium. The control program can also be provided over the Internet or other computer network for downloading and storage to a storage medium in or connected to the user""s computer or printing apparatus from which the program is used.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.